American Board of Internal Medicine (ABIM) Certification Practice Exam

What is typically indicated by a significantly elevated prolactin level (>200 ng/mL)?

1. A normal physiological response

2. A possible prolactinoma

3. Stress-related hyperprolactinemia

4. A response to neuroleptics

The correct answer is: A possible prolactinoma

A significantly elevated prolactin level, particularly above 200 ng/mL, is most commonly indicative of a prolactinoma, which is a benign tumor of the pituitary gland that secretes excessive amounts of prolactin. This condition is characterized by hyperprolactinemia, leading to symptoms such as galactorrhea (breast milk production), amenorrhea (absence of menstruation), and fertility issues in women, as well as decreased libido and erectile dysfunction in men. While other conditions can cause elevated prolactin levels, the degree of elevation seen with levels over 200 ng/mL strongly points towards a prolactinoma. For example, physiological causes of elevated prolactin, such as pregnancy or breastfeeding, typically do not reach this high level. Similarly, stress and the use of certain medications, like neuroleptics, can also lead to increased prolactin levels, but these causes are often less severe and would not usually present with such extreme values. Therefore, a prolactin level consistently above 200 ng/mL warrants further investigation for a prolactinoma as the most likely underlying cause.